Mariska M. H. P. Janssen

Design and pilot validation of A-gear: a novel wearable dynamic arm support

BackgroundPersons suffering from progressive muscular weakness, like those with Duchenne muscular dystrophy (DMD), gradually lose the ability to stand, walk and to use their arms. This hinders them from performing daily activities, social participation and being independent. Wheelchairs are used to overcome the loss of walking. However, there are currently few efficient functional substitutes to support the arms. Arm supports or robotic arms can be mounted to wheelchairs to aid in arm motion, but they are quite visible (stigmatizing), and limited in their possibilities due to their fixation to the wheelchair. The users prefer inconspicuous arm supports that are comfortable to wear and easy to control.MethodsIn this paper the design, characterization, and pilot validation of a passive arm support prototype, which is worn on the body, is presented. The A-gear runs along the body from the contact surface between seat and upper legs via torso and upper arm to the forearm. Freedom of motion is accomplished by mechanical joints, which are nearly aligned with the human joints. The system compensates for the arm weight, using elastic bands for static balance, in every position of the arm. As opposed to existing devices, the proposed kinematic structure allows trunk motion and requires fewer links and less joint space without compromising balancing precision.The functional prototype has been validated in three DMD patients, using 3D motion analysis.ResultsMeasurements have shown increased arm performance when the subjects were wearing the prototype. Upward and forward movements were easier to perform. The arm support is easy to put on and remove. Moreover, the device felt comfortable for the subjects. However, downward movements were more difficult, and the patients would prefer the device to be even more inconspicuous.ConclusionThe A-gear prototype is a step towards inconspicuousness and therefore well-received dynamic arm supports for people with muscular weakness.

Surface EMG to assess arm function in boys with DMD: a pilot study.

INTRODUCTION Preserving functional abilities of the upper extremities is a major concern in boys with Duchenne Muscular Dystrophy (DMD). To assess disease progression and treatments, good knowledge on arm function in boys with DMD is essential. Therefore, feasibility and validity of the use of surface electromyography (sEMG) to assess arm function in boys with DMD was examined. METHODS Five boys with DMD and 6 age-matched controls participated in this study. Single joint movements and ADL activities were examined while recording sEMG of main shoulder and elbow muscles. RESULTS All boys with DMD and controls were able to perform the non standardized movements of the measurement protocol, however one boy with DMD was not able to perform all the standardized movements. Boys with DMD used significantly more of their maximal muscle capacity for all muscles to conduct movements compared to controls. DISCUSSION/CONCLUSION The measurement protocol was feasible to assess arm function in boys with DMD. This tool was able to discriminate between DMD patients and controls.

Upper limb function and activity in people with facioscapulohumeral muscular dystrophy: a web-based survey

Abstract Purpose To investigate the upper extremity (UE) at the level of impairments and related activity limitations and participation restrictions in people with facioscapulohumeral muscular dystrophy (FSHD). Methods The study was conducted using web-based questionnaires that were distributed amongst people with FSHD in the Netherlands. Eighty-eight respondents started the survey, and 71 completed it. The questionnaires covered the following dimensions: Function, Activity and Participation of the International Classification of Functioning Disability and Health. Results More than 40% of the respondents experienced pain in one arm or both the arms. Increased pain and stiffness scores and longer disease duration were associated with increased limitation scores. For basic activities, lifting the arm above shoulder-level was most frequently reported as most limited, coherent with the clinical picture of FSHD. Among the respondents, 50% indicated restrictions at school, 78% indicated restrictions at work and more than 80% indicated restrictions whilst participating in sports, hobbies, household activities and romantic relationships. Conclusions This study has shown that alongside the well-known problem of lifting the arms above shoulder-level, UE activities below shoulder height during vocational and occupational activities are also problematic in patients with FSHD. Alongside disease duration, pain and stiffness are associated with UE activity limitations. Implications for Rehabilitation Attention is needed for pain and experienced stiffness in the upper extremity as it is frequently present in patients with FSHD. Rehabilitation professionals need to be aware that patients with FSHD not only experience problems with activities above shoulder height, but also with activities below shoulder height. At least 50% of the patients with FSHD experience restrictions in participation as a result of limitations in their UE.

Different profiles of upper limb function in four types of neuromuscular disorders

The aim of this research was to study impairments, activity limitations and participation restrictions due to upper limb involvement in people with four different types of neuromuscular disorders (NMD) - FacioScapuloHumeral Dystrophy (FSHD), Limb-Girdle Muscular Dystrophy (LGMD), Spinal Muscular Atrophy (SMA) and Duchenne Muscular Dystrophy (DMD) - and to investigate whether common or different profiles could be identified. Total of 267 respondents with NMD from the Netherlands answered a set of questionnaires covering upper limb impairments (pain and stiffness), activity limitations and participation restrictions. Pain was most often reported by persons with FSHD. Problems in the FSHD group were mainly characterized by relatively high scores for pain and stiffness and low scores for activity limitations. People with LGMD reported also low scores for activity limitations. Conversely, people with SMA and DMD experienced in general relatively low scores for pain and stiffness and high scores for activity limitations. Although people with FSHD and LGMD had relatively few activity limitations, all NMD groups experienced restrictions when participating in social activities. Our results indicate specific profiles of upper limb function in different types of NMD. While the profile observed in persons with FSHD seems to reflect overuse, the profile seen in persons with DMD and SMA is suspicious of disuse, each requiring a specific rehabilitation strategy.

Towards a short questionnaire for stepwise assessment of upper limb function, pain and stiffness in Duchenne muscular dystrophy

Abstract Purpose: Duchenne muscular dystrophy can lead to upper extremity limitations, pain and stiffness. In a previous study, these domains have been investigated using extensive questionnaires, which are too time-consuming for clinical practice. This study aimed at gaining insight into the underlying dimensions of these questionnaires, and to construct a short questionnaire that can be used for clinical assessment. Methods: Exploratory factor analysis was performed on the responses of 213 participants to a web-based survey to find the underlying dimensions in the Capabilities of Upper Extremity questionnaire, the ABILHAND questionnaire, and questionnaires regarding pain and stiffness. Based on these underlying dimensions, a stepwise approach was formulated. In addition, construct validity of the factors was investigated. Results: In total, 14 factors were identified. All had high internal consistency (Cronbachs alpha >0.89) and explained 80–88% of the variance of the original questionnaires. Construct validity was supported, because participants in the early ambulatory stage performed significantly better (p< 0.001) than participants in the late non-ambulatory stage. Conclusion: The factors identified from the set of questionnaires provide a valid representation of upper extremity function, pain and stiffness in Duchenne muscular dystrophy. Based on the factor commonalities, the Upper Limb Short Questionnaire was formulated. Implications for Rehabilitation New insights into the underlying dimensions of upper extremity function, pain and stiffness in Duchenne muscular dystrophy are gained. Fourteen factors, with good internal consistency and construct validity, are identified regarding upper extremity function, pain and stiffness in Duchenne muscular dystrophy. Based on these factors, the Upper Limb Short Questionnaire is presented. The Upper Limb Short Questionnaire can be used as an identifier of arm-hand limitations and the start of more thorough clinical investigation.

Design and control of the Active A-Gear: A wearable 5 DOF arm exoskeleton for adults with Duchenne muscular dystrophy

Adults with Duchenne muscular dystrophy (DMD) can benefit from active arm supports that augment the residual motion capabilities of their arms. While there is a considerable number of active exoskeletons commercially available for rehabilitation purposes, no active exoskeletons for supporting the arm function during the performance of activities of daily living (ADL) are available. In this paper, we present the Active A-gear, a wearable five degree-of freedom exoskeleton that has been specially developed to assist people with DMD for the performance of ADL. The Active A-Gear is built upon our previous design of the passive A-Gear, thus combining active and passive support. The Active A-Gear can be controlled using force-based (admittance) control. We report the results of the system verification, which included endpoint position bandwidth, workspace, weight, joint speed, endpoint force and joint backlash measurements. A pilot evaluation was carried out with one healthy subject (27 years-old) performing ADL. The results of the verification and evaluation tests indicate that with some modifications the Active A-Gear is a suitable platform to test the functional performance and feasibility of a wearable and active support for adults with DMD.

A Novel Setup and Protocol to Measure the Range of Motion of the Wrist and the Hand

The human hand is important for the performance of activities of daily living which are directly related to quality of life. Various conditions, such as Duchenne muscular dystrophy (DMD) can affect the function of the human hand and wrist. The ability to assess the impairment in the hand and the wrist by measuring the range of motion (ROM), is essential for the development of effective rehabilitation protocols. Currently the clinical standard is the goniometer. In this study we explore the feasibility and reliability of an optical sensor (Leap motion sensor) in measuring active hand/wrist ROM. We measured the hand/wrist ROM of 20 healthy adults with the goniometer and the Leap motion sensor, in order to check the agreement between the two methods and additionally, we performed a test-retest of the Leap motion sensor with 12 of them, to assess its reliability. The results suggest low agreement between the goniometer and the leap motion sensor, yet showing a large decrease in measurement time and high reliability when using the later. Despite the low agreement between the two methods, we believe that the Leap motion sensor shows potential to contribute to the development of hand rehabilitation protocols and be used with patients in a clinical setting.

Dynamic arm study: quantitative description of upper extremity function and activity of boys and men with duchenne muscular dystrophy

BackgroundTherapeutic management of upper extremity (UE) function of boys and men with Duchenne Muscular Dystrophy (DMD) requires sensitive and objective assessment. Therefore, we aimed to measure physiologic UE function of healthy subjects and DMD patients in different disease stages, and to evaluate the relation between these physiologic measures and functional UE scales.MethodsTwenty-three DMD patients and twenty healthy controls (7–23 years) participated in this explorative case–control study. Maximal muscle torque, maximal and normalized surface electromyography (sEMG) amplitudes, muscle thickness, echogenicity and maximal passive and active joint angles were measured. At activity level, Brooke upper extremity rating scale and the Performance of Upper Limb (PUL) scale were used.ResultsOutcome measures related to proximal UE function could discriminate between disease stages. Increased normalized sEMG amplitudes were found in patients, even in early disease stages. Maximal active joint angles showed the strongest relation to Brooke scale (R2 = 0.88) and PUL scale (R2 = 0.85).ConclusionsThe decline of muscle functions precedes the decline in performance of UE activities, and therefore may play a role in early detection of UE limitations. Increased sEMG levels demonstrate that DMD patients use more of their muscle capacity compared to healthy subjects, to perform daily activities. This might result in increased fatigability. Active maximal joint angles are highly related to functional scales, so preserving the ability to use the full range of motion is important for the performance of daily activities. Close monitoring of active joint angles could therefore help in starting interventions that minimize functional UE decline in DMD patients timely.

Surface EMG signals in very late-stage of Duchenne muscular dystrophy: a case study

BackgroundRobotic arm supports aim at improving the quality of life for adults with Duchenne muscular dystrophy (DMD) by augmenting their residual functional abilities. A critical component of robotic arm supports is the control interface, as is it responsible for the human-machine interaction. Our previous studies showed the feasibility of using surface electromyography (sEMG) as a control interface to operate robotic arm supports in adults with DMD (22-24 years-old). However, in the biomedical engineering community there is an often raised skepticism on whether adults with DMD at the last stage of their disease have sEMG signals that can be measured and used for control.FindingsIn this study sEMG signals from Biceps and Triceps Brachii muscles were measured for the first time in a 37 year-old man with DMD (Brooke 6) that lost his arm function 15 years ago. The sEMG signals were measured during maximal and sub-maximal voluntary isometric contractions and evaluated in terms of signal-to-noise ratio and co-activation ratio. Beyond the profound deterioration of the muscles, we found that sEMG signals from both Biceps and Triceps muscles were measurable in this individual, although with a maximum signal amplitude 100 times lower compared to sEMG from healthy subjects. The participant was able to voluntarily modulate the required level of muscle activation during the sub-maximal voluntary isometric contractions. Despite the low sEMG amplitude and a considerable level of muscle co-activation, simulations of an elbow orthosis using the measured sEMG as driving signal indicated that the sEMG signals of the participant had the potential to provide control of elbow movements.ConclusionsTo the best of our knowledge this is the first time that sEMG signals from a man with DMD at the last-stage of the disease were measured, analyzed and reported. These findings offer promising perspectives to the use of sEMG as an intuitive and natural control interface for robotic arm supports in adults with DMD until the last stage of the disease.

Comparison between sEMG and force as control interfaces to support planar arm movements in adults with Duchenne: a feasibility study

BackgroundAdults with Duchenne muscular dystrophy (DMD) can benefit from devices that actively support their arm function. A critical component of such devices is the control interface as it is responsible for the human-machine interaction. Our previous work indicated that surface electromyography (sEMG) and force-based control with active gravity and joint-stiffness compensation were feasible solutions for the support of elbow movements (one degree of freedom). In this paper, we extend the evaluation of sEMG- and force-based control interfaces to simultaneous and proportional control of planar arm movements (two degrees of freedom).MethodsThree men with DMD (18–23 years-old) with different levels of arm function (i.e. Brooke scores of 4, 5 and 6) performed a series of line-tracing tasks over a tabletop surface using an experimental active arm support. The arm movements were controlled using three control methods: sEMG-based control, force-based control with stiffness compensation (FSC), and force-based control with no compensation (FNC). The movement performance was evaluated in terms of percentage of task completion, tracing error, smoothness and speed.ResultsFor subject S1 (Brooke 4) FNC was the preferred method and performed better than FSC and sEMG. FNC was not usable for subject S2 (Brooke 5) and S3 (Brooke 6). Subject S2 presented significantly lower movement speed with sEMG than with FSC, yet he preferred sEMG since FSC was perceived to be too fatiguing. Subject S3 could not successfully use neither of the two force-based control methods, while with sEMG he could reach almost his entire workspace.ConclusionsMovement performance and subjective preference of the three control methods differed with the level of arm function of the participants. Our results indicate that all three control methods have to be considered in real applications, as they present complementary advantages and disadvantages. The fact that the two weaker subjects (S2 and S3) experienced the force-based control interfaces as fatiguing suggests that sEMG-based control interfaces could be a better solution for adults with DMD. Yet force-based control interfaces can be a better alternative for those cases in which voluntary forces are higher than the stiffness forces of the arms.